Rotary gear-type metering pump



De?u 29 H950 n D, R, HULL, Elf-AL 2533,32

ROTARY GEAR TYPE METERING PUMP Filed Jan. 4;-, 1949 O ll ATTORNEYPatented Dec. l2, 1950 UNITED STATES PATENT OFFICE ROTARY GEAR-TYPEMETERING PUMP Application January 4, 1949, Serial No. 69,082

1 Claim.

This invention relates to improvements in precision liquid advancingpumps and more particularly to improvements in rotary metering pumps ofthe gear type adapted for use in advancing twin streams of a viscousliquid at a substantially constant rate.

Frecision rotary pumps and particularly precision gear pumps have longbeen used for pumping and metering filament-forming compositions tospinnerets and the like in the rayon industry. Such pumps are suitablefor forwarding the viscous compositions in a constant amount per unittime with great accuracy. These precision pumps with their attendantdrives are very expensive and a considerable item of maintenance,

` and, where a separate pump is used for each spinning position, thespace requirement factor is also of serious concern.

To conserve space a common concept in the past has been to divide thepump out-put or to utilize a single pump to deliver two streams of theliquid being metered. In general, this procedure has taken two courses.One method has been to use three or more intermeshing gears so arrangedthat a plurality of streams of material may be delivered therefrom.Another procedure has been the use of a pair of intermeshing gears witha conventional outlet, and, as a secondary outlet, discharge ports atthe base of each tooth of the driven gear, whereby the meshing of thegears forces the entrapped portion of the liquid caught between thegears through said discharge ports in much the same manner as a pistonoperatesto force liquid from its associated cylinder. The dischargeports in turn discharge into the hollow arbor of the driven gear andthence to a suitable supply line. Because of the normally viscous natureof spinning compositions, however, such modifications have not beensuccessful in feeding equal amounts of material to each article-formingdevice. Furthermore, material supplied by the secondary outlet wouldpulsate in such a manner as to produce, in the case of spinning, a verynon-uniform ber. Consequently, it has been necessary to utilizeindividual pumps for each spinning position separately geared to acommon drive.

An object of this invention therefore is to provide an improved rotary,gear-type metering pump.

Another object is to provide a rotary gear-type vmetering pump operativeto deliver two streams of a viscous liquid at a substantially uniformrate.

Still another object is to provide a compact precision metering pump forsupplying lamentforming material to two spinning positionssimultaneously.

A still further object is to provide an improved rotary, gear-typemetering pump which will afford overall savings in space, and ininvestment and maintenance costs.

These and other objects will more clearly appear hereinafter.

These objects are realized by our invention which will now be describedwith reference to the accompanying drawings wherein the legends refer tolike parts referred to in the description, and wherein;

Figure 1 is an elevational view of the side of a preferred embodiment ofthe invention showing the assembly of the plates forming the gear pumphousing.

Figure 2 is an elevational view of the front face of the gear pumphousing assembly shown in Figure 1. w

Figure 3 is a vertical cross-section on the line 3-3 of Figure 7, of theplateforming the peripheral wall of the liquid-forwarding gears.

Figure 4 is an elevational view of one face of the middle plate of thegear pump housing assembly.

Figure 5 is an end view of the middle plate of the gear pump housingassembly.

Figure 6 is a vertical cross-section on the line I-I of Figure 2.

Figure 7 is a horizontal cross-section on the line 2--2 of Figure 2.

Figure 8 is a detail, partly in section of the xed shaft of the gearpump.'

Referring to Figure 1, the gear pump housing assembly comprises a frontor face plate designated by the numeral I, intermediate or gear plates 2and 4, and a rear or back plate 5. The ve plates are held together,preferably, by bolts or screws shown in Figure 6. A set of meshingliquid-forwarding gears comprising driving gear 6 and driven gear 'I areoperatively positioned within the generally circular openings 8 and 9(Figures 3 and 7) provided therefor in gear plate 2, and between faceplate I and middle plate 3. A second set of meshing liquid-forwardinggears comprising driving gear I0 and driven gear II are positioned inlike manner in openings I2 and I3 in gear plate 4, and between themiddle plate 3 and the back plate 5, (each pair of meshing gears may behoused within a plate which serves the purpose of a gear plate and oneside plate, whereby to form a housing assembly of three plates insteadof ve plates). The driving gears 6 and I0 are keyed or otherwisesuitably fixed on assasao 3 the split drive shaft I4 (rotated atconstant speed by any suitable means not shown) journaled in bearingsI5, I6 and I1 provided in plates l, 3 and respectively, and the drivengears 1 and II are mounted for free rotation about a xed shaft or arborI8 fitted in holes I9, 20 and 2| of plates I, 3, and 5 respectively.

A liquid inlet channel to the inlet or low pressure side of each pair ofmeshed gears is provided by the registering openings 22 and 23 in platesI and 3, respectively, and by the arcuate recessed openings (opening 24,Fig. 3) in plates 2 and A liquid outlet from the delivery or highpressure side of meshed gears 6 and 1 is provided by the arcuaterecessed opening 25 (which is smaller than opening 23) in plate 2 and bythe opening 26 connecting therewith in plate I. An outlet from thedelivery side of meshed gears I0 and II is formed by an arcuate recessedopening in plate 4 (identical with opening 25 in plate 2), and aconnecting groove 21 in plate 3 which groove in turn registers with apassageway 28 formed in shaft I8 (Figure 8).

In operation, the liquid to be forwarded by the pump enters at the inletport or opening 22, either by gravity or from a booster pump, passesthrough plate I and thence to the low pressure or inlet side of gears 6and 1 at 24, and through the opening 23 in plate 3 to the low pressureor inlet side of gears I0 and II. A portion of this liquid is entrappedby meshing gears 6 and 1 and carried around the periphery of theopenings 8 and 9 to the high pressure or outlet side of these gears fromwhere it passes through opening 26 in the face plate and is delivered toa suitable spinning device. The remainder of the liquid at the inletside of the pump is entrapped by gears I0 and II and is carried (in thepockets formed between the gear teeth) around the periphery of openingsI2 and I3 to the high pressure side of these gears from which point itis forced in turn through groove 21 and passageway 28 to the outside ofthe pump and is delivered to a second suitable spinning device. Theliquid fed into the pump is thus delivered in two substantially equaland independent streams.

The following specific example is further illustrative of the operationand preferred application of the device of this invention:

Molten polyhexamethylene adipamide having a relative viscosity of aboutis delivered at 20 p. s. i. and 275 C. to the inlet port 22 of the pumpconstruction hereinabove described. The pump operates to give two equal,accurately metered streams of 1.1 grams of melt per revolution per pump,as per the preceding description. The two streams of molten polymerdelivered at the outlet ports are each forced through a suitablefiltering device under a pressure of the order of 2,000 p. s. i. to two20-hole spinnerets each at the rate of 22.07 gm./min. of polymer. Fromeach spinneret there is obtained uniform 240 denier- 20 filament yarn atthe rate of 980 yds/min. Both yarns are identical in every respect.

A pump of the type described herein is especially adapted for themelt-spinning of synthetic linear polyamides, since it is capable ofdelivering very viscous liquids at high pressures. However, it is, ofcourse, entirely suitable for delivering less viscous liquids at lowerpressures. As examples of some filament-forming compositions which maybe handled by such a pump, either in the molten state or as solutions,might be mentioned synthetic linear polyamides, polyesters, polyethers,polyacetals and mixed polyester-amides such as may be prepared bycondensation reactions as described in U. S. Patent 2,071,250 or othersynthetic polymers such as ethylene polymers, vinyl polymers, such aspolystyrene and polyacrylonitrile, polyacrylic acid derivatives,solutions of cellulose esters or cellulosic solutions such as viscose orcuprammonium cellulose and others.

In general, the pump of this invention will operate eiciently withliquids, for example solutions or melts of lament-forming compositionsof 25 poises viscosity or greater. 3,000 poise or still higher viscositymelts of nylon can be readily metered by means of this pump. The onlylimitations as to maximum viscosity is that the liquid be able to ow orbe forced into the pump.

For extrusion of film or filament-forming compositions at hightemperatures and especially where the composition is of a corrosivenature at these temperatures, e. g., in the melt extrusion of polymericmaterials such as synthetic linear polyamides, the choice of a suitablematerial of construction for these pumps becomes of considerableimportance. For these purposes it has been found that the essentialcharacteristics are resistance to corrosion, resistance to abrasion andgalling, together with a low thermal expansion characteristic after theparts that go to make up the pump have been heat-treated. It has beenconcluded that for certain purposes, such as the melt-spinning of nylon,this combination of properties can best be obtained by using steelscontaining in the range of 10%-l6% chromium, 1%1.6% carbontogether withother elements which may be added, such as cobalt, vanadium andmolybdenum. Other suitable steels are those such as air-hardened diesteels and nitrided Nitralloys, in which a steel containing combinationsof chromium, molybdenum and vanadium with the addition of small amountsof nickel, cobalt or aluminum is heated in a nitriding atmosphere toachieve case-hardening. Non-ferrous temperature-resistant alloys, suchas Stellite (a commercial alloy of chromium, molybdenum, nickel andiron), are also useful.

It is recognized as being desirable to employ heat-treatment on themachined parts such that any tendency to distort or warp in service,vthereby causing binding or leakage, may be minimized. This relativefreedom from distortion in service may be accomplished by rapid coolingfrom the hardening temperature in air or by immersion in oil, whichcooling is followed at once by a drawing operation in the uppertemperature range of the 600 F.-1200 F. interval with approximately 800F.1000 F. preferred.

Although the pump of this invention has been described with reference tothe extrusion of film or iilament-forming compositions, it is alsoapplicable to the metering ofcompositions in the spinning of bristlesand the coating of wire, etc. The advantages of the apparatus of thisinvention are obvious, since by use of a single driven shaft and asingle liquid supply duct, it is possible to obtain, at equal rates,delivery to two article-forming mechanisms. This is accomplished by aninexpensive and compact apparatus, the maintenance of which is muchlower than two separate pumps as well as having a lower powerconsumption. Further, the pumps of the prior art normally used todeliver two equal stream of liquid, i. e., three-gear pumps do not meteras accurately as the pumps of this invention. As an additionaladvantage, the pump driven liquid-forwarding gear meshed therewith,

the drive gears being fixed to a common rotatable drive shaft forrotation therewith and the driven gears being mounted for free` rotationon a common fixed shaft parallel to the drive shaft, a housing for saidgears comprising a face plate disposed to serve as a front sidewall ofthe housing for the rst of said sets of gears, a second plate cut outand disposed to serve as the peripheral wall of the housing for said rstset 0f gears, a third plate disposed to serve as a rear side Wall forthe said rst set of gears and as a front side wall of the housing forthe other set of gears, a fourth plate cut out and disposed to serve asthe peripheral wall of the housing for said other set of gears, and aback plate disposed to said other set of gears, the face plate, thethird serve as the rear side wall of the housing for I plate and theback plate having aligned openings into which are tted the drive shaftand the fixed shaft, aligned openings in the face plate and in the thirdplate positioned to afford a passageway for liquid to the gears, anopening in the face plate positioned to aiord a passageway for liquidforwarded by said rst set of gears and liquid outlet means for saidother set of gears comprising a groove in said third plate positioned toaiTord a passageway for liquid forwarded by said other set of gears fromsaid gears to the xed shaft and a connecting passgeway in said xed shaftextending to and through the front end of said fixed shaft and throughsaid face plate.

DONALD ROBERT HULL. DANIEL PARKER PHILLIPS. NELSON HALL TATE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

